Hoist



Sept. l9, 1933. v P; HEIL j 1,927,031

' HOIST Filed on. 11, 1950 2 Sheets-Sheet 1 m mvroa y mam A TI'GPNEY.

Sept. 19, 1933.

J. P. HElL 1,927,031

HOIST Filed 051.11, 1930 2 Sheets-Sheet 2 A TTORNEY.

Patented Sept. 19, 1933 UNITED STATES HOIST Julius 1. Hell, Milwaukee,Wis" assignor to The Hell 00., Milwaukee, Wis., a corporation ofWisconsin Application October 11, 1936. Serial No. 487,982

1 Claim.

The present invention relates in general to improvements in the art ofraising and lowering objects, and relates more specifically toimprovements in the construction and operation of hoists 5 of the fluidpressure actuated type.

Generally stated, an object of the invention is to provide an improvedfluid pressure operated hoist which is simple and compact inconstruction, and'which is moreover highly eiiicient in operation.

' As shown and described in Patent No. 1,594,728, granted August 3rd,1926, it has heretofore been proposed to utilize one or more hoistingdevices, each comprising a cylinder having an upper end head and apiston movable within the cylinder by oil under pressure, and having arod slidable through an opening in the cylinder head, for

various purposes such as raising and lowering the tiltable body of adump truck. The prior hoisting devices of this type employ a pump forforcing a predetermined quantity of oil beneath the piston in order toraise the latter, and a stop sleeve embracing the piston rod closelyadjacent to the piston, is cooperable with the cylinder end head for thesole purpose of preventing the piston sealing rings from leaving theupper end of the cylinder bore, in case the piston is excessivelyelevated by some extraneous force other than the oil pressurethereunder.

In these prior hoists the maximum oil pressure obtainable by the pumpfor delivery beneath the piston is insufllcient to raise the latter sothat the stop sleeve will engage the cylinder head, and a port whichshould not be exposed during normal lifting of the piston, communicateswith the upper interior of the cylinder andwith a passage formed withinthe pump so as to permit return of oil from beneath the piston to thespace thereabove during lowering operation. In order to reduce thelength of the cylinder to a minimum, thetreturn port has heretofore beenso positioned, that under certain abnormal conditions of operation suchas sudden shifting of the load in the truck body during dumping, thepiston and its stop sleeve might be lifted to bring the latter intodirect engagement with the head. thereby in some cases momentarilyslightly exposing the lower portion of the return port, to the spacebeneath the piston, and allowing a small quantity of oil to leak intothe pump. Such leakage of oil due to unintentional exposure of thereturn port, is undesirable, since it interferes with maintaining thepiston in fixed position after theelevating stroke has been completed,and also because it permits rather violent impact between the stopsleeve and the cylinder head under abnormal operating conditions such ashereinabove described.

It is a more specific object of the present invention to provide meansfor eifectively overcoming these defects of the prior art hoists of thistype, by positively preventing any tendency toward free escape of oilfrom beneath the piston when elevated, and until the operator is readyto lower the hoist.

Another object of the invention is to provide a fluid pressure operatedhoist pf the type generally described wherein the use of a special stopsleeve for the piston is avoided, thereby simplifying the structurewithout sacrificing efiiciency (0 in operation.

These and other objects and advantages will appear from the followingdetailed description.

A clear conception of an embodiment of the novel features constitutingthe present invention f5 and of the mode of constructing and ofoperating hoists built in accordance therewith, may be had by referringto the drawings accompanying and forming a part of this specification inwhich like reference characters designate the same or similar parts inthe various views:

Fig. 1 is a side elevation of a truck having a tiltable dump bodyoperable by hoisting mechanism of the improved type, the body beingshown in loading position; 35

Fig. 2 is a side elevation of the dump truck, the body being shown intilted or unloading position:

Fig. 3 is a central vertical section through one of the improvedhoisting cylinders, the piston being shown in lowered position;

Fig. 4 is a fragmentary central vertical section through the hoistcylinder, the piston being shown in normal elevated position; and

Fig. 5 is a central vertical section through the pump for supplyingfluid pressure beneath the piston of the hoist for elevating purposes.

Referring to Figs. 1 and 2 of the drawings, the tiltable truck body 6 ispivotally mounted upon the rear portion of the truck chassis or frame 7,by means oi a pivotal support 8, the forward portion of the body 6 beingswingable about the rear pivotal support and in close proximity to thedriver's cab 9, by means of one or more fluid pressure actuating hoistscoacting with a medial lower por-- tion of the tiltable body 6.

Each of the hoists shown in detail in Figs. 3 and 4, comprises ingeneral a cylinder 10 having side trunnions pivotally supported insaddles 11 secured to the truck frame I and a piston 14 and rod 12movable along the cylinder bore. The piston rod 12 of each hoist isslidable through a packing associated with the removable upper end head15 of the cylinder 10, and has its upper end secured directly to thebody 6 by means of a pivotal connection 13. With this assemblage andmounting of the elements, the introduction of fluid such as oil underpressure, beneath the lower face of the piston 14, causes the upwardlymoving rod 12-to swing the truck body 6 upwardly about the rear pivotalsupport 8, as shown in Fig. 2, whereas release of the fluid pressurewill cause the body 6 to move back into horizontal position as shown inFig. 1, the saddle supports and the pivotal connection 13 serving topermit lateral tilting of the hoist during tilting of the truck bodyrelative to the frame.

The displacement chamber 18 beneath the piston 14, communicates with thelower end of an elongated port 19 formed directly in the wall of thecylinder 10, and the upper end of the port 19 communicates with aconduit 20 formed in a manifold 37 secured to the upper portion of thecylinder head. The fluid storage and receiving space 17 above the piston14, communicates with an annular conduit or passage 25 formed in thecylinder 10, through a port 26 and a conduit 2'1 having a check valve 28therein and connecting the passage 25 with the extreme upper end of thespace 17. The annular passage 25 communicates with aconduit 22 formed inthe manifold 37, through a port 24 disposed on the side of the cylinder10.,opposite to the port 26.

As shown in Fig. 5, the manifold 37 also forms the base of a gear pump16, and has a set of ports 20', 22 extending laterally from the con-.riuits 20, 22 respectively, into a casing 42 having arotaryby-passvalve 21 therein. The valve 21 is operable by a'leve'r 23 andactuating rod 31 to either establish direct communication betweenv theconduits 20, 22 through the ports 20', 22' in order to permit-fluid toflow from the chamber 18'to thespace 17, or to cut-oil suchcommunication. The'inanifold 3'7 is moreover provided with a setof'ports; 20", 22" extending laterally from the conduits20,'22respectively, to the displacement chamber of thepump 16', the port 20"constituting the pump discharge passage and the port 22" being the pumpsuction. Located within the discharge passage or port 29", isa dischargevalve 30, past which the fluid is. delivered by-the rotors 29 of thepump 16, when the control'valve 21.

is positioned as shown in Fig, 5. One of the intermeshing pump rotors291s rotatable by means of a drive shaft 32 which is operable from thetransmission mechanism 35 of the truck,

through a telescopic drivingconnection 33 and. control mechanism 34, thelatter being-operable from within the .cab 9 by means of suitablecontrolling devices 36 which also serve to controlv the operation of theby-pass valve 21.

The piston 14 is provided with resilient scal ing rings 38 oi! us I 39of the piston may be extended beyond the. upper end of the bearingsurface to provide a stop for the piston 14 under certain abnormalconditions of operation. During normal operation, the upward travel ofthe piston .14 within the bore of the cylinder 10, is limitedto theposition indicated in Fig. 4, but under abnormal conditions of operationsuch as shifting of the load within the body 6 during dumping, thepiston rod 12 and the piston 14 associated therewith may be pullingupwardly within the cylinder 10 and away from the oil body in thedisplacement cham-- ual construction, and the hub" .17, and the apron ofthe piston 14, which sur rounds the hub 39, should not be of suflicientheight to interfere with the vent 41 or to seal the passage 27. The vent41 comprises a casing having a large lower bore 42 in which a ballcheck; 43 is freely vertically movable, and. also having a reduced upperbore 44 which communicates with the atmosphere through a lateral hole45.

-The ball check 43 which is confined within the lower bore 42 is ofsomewhat less diameter than this confining bore, but is of greaterdiameter than the upper bore 44, so that any oil attempting to escapewith the air willautomatically cause the ball check 43 to seat againstthe lower end of the bore 44 to thereby close the vent and prevent lossof oil from the system.

During normal operation of the truck, the body 6 is in lowermostposition as shown in Fig. 1, while being loaded and also while beingtransported by the vehicle, but the body 6 may at any time be tilted 'tothe position shown in Fig. 2 by operation of the hoist. In order to tiltthe body 6 relative to the frame 7, it is only necessary for theoperator to place the truck propelling motor in operation and tomanipulate the control devices 36 within the cab 9. After the gear pump16 has been drivingly connected to the transmission mechanism 35, therod 31 and lever 23 may be actuated to position the valve 21 as shown inFig. 5, whereupon the pump 16 will withdraw oil from the space 1'1through the port 26, passage 25, port 24, conduit 22 and port 22", andwill force the oil past the discharge valve 30 and through the port 20",conduit 20 and port 19 into thedisplacement chamber 18 beneath thepiston 14. This introduction of oil under pressure beneath the piston,causes the same to rise and to simultaneously tilt the truck body 6, andcontinues until the piston 14 reaches its upper'position as shown inFig. 4, whereupon the supply of oil from the space 17 above the pistonthrough the port 26, has been cut off by the annular apron surroundingthe piston hub 39, thus preventing the pump 18 from withdrawing any moreoil from above the piston. While this supply of oil from the space 1'!is cut oil? immediately as the piston apron passes the port 26, the pumpcontinues to withdraw oil from the passage 25, port 24 and conduit 22and to force this oil beneath the piston 14, thus causing the upperendof the piston to travel some distance beyond the port 26, but not toa sufiicient extent that thehub 39 will engage the abutment 40 of thecylinder-head 15. Such engagement between a the hub: 39 andj, theabutment 40, occurs only when "the piston moved upwardly beyond itsnormal str'ohe by some extraneous force, and even when thus.abnormaily'elevated, the lower end of the pistonTldwill not uncoverthe,port 26. During such he or abnormalgupward movement of the piston,[excess air-conflned .withln the space 17 above thepistgn 14, will bedischarged through the .vent 41 in themanner previously described, butthe ball clieck,,4S;prevents escapee! 'oilwith the air. Due to theiaetthatthe pump idcannot discharge all of the oil mus ums. the conduits andpassages at the inietside while the piston 14 is elevated and maintstnedinelevated condition, there will be a small quantity of oil constantlycirculated within the pump, and this retained oil will serve tolubricate the pump rotors 29 and will prevent overheating of the pump.

If it becomes desirable to lower the truck body 6, it is only necessaryto move the actuating lever 23 of the valve 21 toward the left as viewedin Fig. 5, whereupon the valve 21 establishes communication through theports 20', 22', between the conduits 20, 22 respectively, in the pumpbase. The weight of the truck body 6 and of the elements carriedthereby, will then cause the piston 14 to move downwardly within thecylinder bore and to force the oil from the displacement chamber 18through the port 19, conduit 20, passage 20', valve 21, passage 22',conduit 22, port 24, annular passage 25, passage 2'7 and port 26, intothe storage space 17 above the piston 14. The descent of the piston 14will continue until the piston reaches the position shown in Fig. 3, andthe pump 16 may obviously bemaintained in operation, if so desired,while the piston 14 is being lowered. The check valve 28 serves topermit initial introduction of oil to the space 17 above the piston 14during the lowering operation, but this check valve will not permit airto be withdrawn from the space 17 by the pump 16.

It should be borne in mind that the purpose of providing the elongatedhub 39 and the abutment 40 cooperable therewith during abnormal upwardtravel of the piston 14, is not merely to stop the piston 14 and the rod12 during their upward travel, but is primarily for preventing thepiston 14 from being lifted suiliciently to permit" the upper packingring 38 to leave its retaining. groove, The quantity of oil which thepump 16 is permitted to force into the displacement chamber 18 shouldnever be suilicient to cause the piston hub 39 to strike the abutment40, but should only be sufficient to cause the piston 14 to travelupwardly to the limiting posi tion indicated in 'Fig. 4. The bearingface of the piston 14 should moreover be of suilicient length topositively prevent uncovering of the port 26 by the lower portion of thepiston during lifting thereof, thereby avoiding any possibility ofhaving oil or fluid under pressure circulate through the port 26 pastthe lower face of the piston. By forming the conduits 20, 22 directly inthe pump base and as an integral part of the pump 16 the construction issimplifled and it becomes unnecessary to provide ,means other than thepump 16 and the piping which connects the pump with the cylinder 10, forestablishing communication between portions of the cylinder 10 above andbelow the piston 14. Hoists manufactured in accordance with the presentimprovements have proven highly successful and efiicient in commercialoperation, and while the actuating fluid has been described hereinspecifically as oil, it will be apparent that other fluids may besubstituted. The improved hoist structure has entirely overcome theobjectionable features encountered in prior hoists of this type, and theconstruction has been considerably simplified by the elimination of thestop sleeves heretofore employed and the substitution of the elongatedpiston hub 39, therefor.

It should be understood that it is not desired to limit the invention tothe exact details of construction herein shown and described, forvarious modifications within the scope of the claims may occur topersons skilled in. the art.

It is claimed and desired to secure by Letters Patent:

In a hoist, an upwardly extending cylinder having upper and lower portscommunicating with the opposite extreme ends thereof and also having anintermediate por't communicating therewith near said upper port, saidcylinder being provided with avbore extending downwardly from saidintermediate port and with an enlarged space above said bore, apistonmovable within said bore, a pump for removing liquid. from said spaceand for delivering said liquid under pressure below said piston throughsaid lower port to cause movement of the piston toward said intermediateport, the quantity of liquid available from said space being onlysuflicient to cause said piston to seal said intermediate port withoutsealing said upper port and said piston being additionally upwardlymovable after complete elevation by said available liquid, means forpositively preventing upward travel of said piston at any timesufllciently to seal-said. upper port and to unseal said intermediateport from below, and vent means for effecting free escape of air fromsaid space while positively preventing escape of liquid with said air. g

' JULIUS P. HEIL.

